// SPDX-License-Identifier: GPL-2.0/* * Test the 'D' (register disabled) flag of binfmt_misc. An entry * registered with it exists but cannot be matched until userspace enables * it, which splits a registration into create and activate. * * Needs root for the registration; no bpf toolchain involved. */#define _GNU_SOURCE#include <stdio.h>#include <stdlib.h> #include "binfmt_misc_common.h"#include "kselftest_harness.h" #define MAGIC		"#DISABLED-SELFTEST#"#define TARGET_PATH	"/tmp/binfmt_disabled_target"#define INTERP_PATH	"/tmp/binfmt_disabled_interp.sh"#define ENTRY		"test_disabled"#define RULE(flags)	":" ENTRY ":M:0:" MAGIC "::" INTERP_PATH ":" flags /* The interpreter exits with a code the harness can recognise. */#define EXIT_INTERP	7 /* The target only has to carry the magic; it is never actually loaded. */static int create_target(void){	char buf[128] = MAGIC "\n";	int fd; 	unlink(TARGET_PATH);	fd = open(TARGET_PATH, O_WRONLY | O_CREAT | O_EXCL, 0755);	if (fd < 0)		return -1;	if (write(fd, buf, sizeof(buf)) != (ssize_t)sizeof(buf)) {		close(fd);		return -1;	}	close(fd);	return 0;} static int create_interp(void){	char buf[64];	int fd; 	unlink(INTERP_PATH);	fd = open(INTERP_PATH, O_WRONLY | O_CREAT | O_EXCL, 0755);	if (fd < 0)		return -1;	snprintf(buf, sizeof(buf), "#!/bin/sh\nexit %d\n", EXIT_INTERP);	if (write(fd, buf, strlen(buf)) != (ssize_t)strlen(buf)) {		close(fd);		return -1;	}	return close(fd);} FIXTURE(disabled) {}; FIXTURE_SETUP(disabled){	if (getuid() != 0)		SKIP(return, "test must be run as root");	if (!binfmt_misc_available())		SKIP(return, "no binfmt_misc"); 	/* Skip the whole suite on a kernel that does not know 'D'. */	if (!binfmt_flag_supported('D')) {		ASSERT_EQ(errno, EINVAL);		SKIP(return, "kernel without the 'D' flag");	} 	ASSERT_EQ(create_interp(), 0);	ASSERT_EQ(create_target(), 0);} FIXTURE_TEARDOWN(disabled){	unregister(ENTRY);	unlink(TARGET_PATH);	unlink(INTERP_PATH);} /* The entry exists but does not dispatch until it is enabled. */TEST_F(disabled, inert_until_enabled){	ASSERT_EQ(write_reg(RULE("D")), 0);	EXPECT_TRUE(entry_shows(ENTRY, "disabled")); 	/* Nothing matches it, so no binary format claims the target. */	EXPECT_EQ(run_payload(TARGET_PATH), RUN_ENOEXEC); 	ASSERT_EQ(entry_command(ENTRY, "1\n"), 0);	EXPECT_TRUE(entry_shows(ENTRY, "enabled"));	EXPECT_EQ(run_payload(TARGET_PATH), EXIT_INTERP);} /* Without 'D' an entry is matchable the moment it is registered. */TEST_F(disabled, enabled_without_the_flag){	ASSERT_EQ(write_reg(RULE("")), 0);	EXPECT_TRUE(entry_shows(ENTRY, "enabled"));	EXPECT_EQ(run_payload(TARGET_PATH), EXIT_INTERP);} /* 'D' is spent on the registration: the entry does not report it back. */TEST_F(disabled, flag_not_reported){	ASSERT_EQ(write_reg(RULE("D")), 0);	EXPECT_FALSE(entry_shows(ENTRY, "flags: D"));	EXPECT_TRUE(entry_shows(ENTRY, "flags: "));} /* A disabled entry can be disabled and enabled like any other. */TEST_F(disabled, toggles_like_any_entry){	ASSERT_EQ(write_reg(RULE("D")), 0); 	ASSERT_EQ(entry_command(ENTRY, "1\n"), 0);	ASSERT_EQ(run_payload(TARGET_PATH), EXIT_INTERP);	ASSERT_EQ(entry_command(ENTRY, "0\n"), 0);	EXPECT_EQ(run_payload(TARGET_PATH), RUN_ENOEXEC);	ASSERT_EQ(entry_command(ENTRY, "1\n"), 0);	EXPECT_EQ(run_payload(TARGET_PATH), EXIT_INTERP);} /* 'D' composes with the invocation flags a static entry can carry. */TEST_F(disabled, composes_with_invocation_flags){	ASSERT_EQ(write_reg(RULE("PD")), 0);	EXPECT_TRUE(entry_shows(ENTRY, "disabled"));	EXPECT_TRUE(entry_shows(ENTRY, "flags: P"));} /* '-1' to the status file sweeps a staged entry with everything else. */TEST_F(disabled, removed_by_remove_all){	int fd; 	ASSERT_EQ(write_reg(RULE("D")), 0);	EXPECT_TRUE(entry_shows(ENTRY, "disabled")); 	fd = open(BINFMT_DIR "/status", O_WRONLY | O_CLOEXEC);	ASSERT_GE(fd, 0);	ASSERT_EQ(write(fd, "-1", 2), 2);	close(fd); 	EXPECT_NE(access(BINFMT_DIR "/" ENTRY, F_OK), 0);} /* A file handle held across a removal cannot resurrect the entry. */TEST_F(disabled, no_resurrection_after_remove){	int fd; 	ASSERT_EQ(write_reg(RULE("D")), 0);	fd = open(BINFMT_DIR "/" ENTRY, O_WRONLY | O_CLOEXEC);	ASSERT_GE(fd, 0); 	ASSERT_EQ(write(fd, "-1", 2), 2);	EXPECT_NE(access(BINFMT_DIR "/" ENTRY, F_OK), 0); 	/* Accepted like any toggle of a removed entry, but publishes nothing. */	EXPECT_EQ(write(fd, "1", 1), 1);	EXPECT_EQ(run_payload(TARGET_PATH), RUN_ENOEXEC);	close(fd);} TEST_HARNESS_MAIN